Detectors 5
Advanced User Guide 85
About the NPD
We strongly recommend that you allow the firmware to perform
Auto Adjust and set the Bead Voltage.
NPD flows and general information
The NPD passes sample and carrier through a hydrogen/air plasma.
A heated ceramic or glass source, called the bead, is just above the jet.
The low hydrogen/air ratio cannot sustain a flame, minimizing
hydrocarbon ionization, while the alkali ions on the bead surface
facilitate ionization of nitrogen- or phosphorus-organic compounds.
The output current is proportional to the number of ions collected. It
is sensed by an electrometer, converted to digital form, and sent to an
output device.
Valve
Frit
Frit
Valve
PS = Pressure Sensor Column
PS
PS PS
Valve
Frit
Restrictor Restrictor
Restrictor
EPC Module
H
2
Air
Vent
Electrically
heated bead
Makeup
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